Rendering software for jewellery design

Really, over what @Cyver has demonstrated above?

Would suggest Keyshot as well, or if cost control is in order, dig into Cycles in V6 ASAP.

https://www.google.com/search?q=keyshot+jewelry&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjZl6jSrtfXAhWEdN8KHRLBCTIQsAQIKg&biw=1232&bih=1521

-my 2 cents